when attempting to add a new port alias [firewall -> aliases -> ports -> add], for example, for mdns [udp port 5353], pfsense complains "The alias name must not be a well-known TCP or UDP port name [...]" [see attached screen shot].

well known ports are 0-1023. if this mechanism is actually checking more than just well-known ports, and is working as intended, to include all official/registered ports in the constraint, it would be best if the feedback conveyed that.